With the development of mobile communication networks and the popularity of mobile user equipment, operators of mobile networks provide not only the basic call services, but also diversified Value-Added Services (VASs) such as the Ring Back Tone (RBT) service and the Customized Ringing Signal (CRS) service.
The IP Multimedia Subsystem (IMS) is a subsystem proposed in the 3rd Generation Partnership Project (3GPP) Release 5 standard to support IP multimedia services. The IMS is based on the Session Initiation Protocol (SIP). SIP is a text-based signaling protocol that works in client-server mode. The IMS uses a SIP call control mechanism to create, manage and terminate various multimedia services.
The CRS service of the IMS domain is subscribed by the caller or the callee and experienced by the callee. When the caller initiates an IMS call to the callee and the callee is capable of receiving IMS calls (for example, the caller or the callee has activated this service), the ring tone of the callee terminal is replaced by the media such as music and video customized by the caller or the callee before the callee answers the call.
If the service is subscribed by the caller, the service is a caller CRS service; if the service is subscribed by the callee, the service is a callee CRS service.
In the conventional art, both the solution of the caller CRS service and the solution of the callee CRS service are available, meeting different individualized requirements of users.
Given below are the two solutions of the CRS service of the IMS domain in the conventional art.
Solution 1: The caller initiates an IMS call to the callee. If the caller or the callee has subscribed the CRS service, the CRS Application Server (AS) adds the Uniform Resource Locator (URL) of a CRS tone to the header field of the initial call request “INVITE” (such as the Call-Info header field). After receiving the INVITE, the callee downloads the CRS tone to a local directory for playing.
Solution 2: The caller initiates an IMS call to the callee. If the caller or the callee has subscribed to the CRS service, the CRS AS performs media negotiation between the Media Resource Server (MRS) and the callee terminal, and instructs the MRS to play the CRS tone to the callee when the callee rings.
If the CRS media is little, the CRS media may be carried in a SIP message directly. After receiving the SIP message, the callee terminal parses the message body and presents the CRS media to the callee.
However, the inventor of the present invention finds that neither the solution to the caller CRS service nor the solution to the callee CRS service in the conventional art specifies how to trigger the CRS service if both the caller and the callee have subscribed to the CRS service. Consequently, the service experience is affected in the case that both the caller and the callee have subscribed to the CRS service.
In addition, the solution to the CRS service in the conventional art provides no function of filtering CRS tones. Therefore, the users can only experience the CRS tones passively, and are not able to select the CRS tones according to their own preferences.